1. Technical Field
The present invention relates to data processing systems, and in particular to migration of data between (I/O) devices. More particularly, the present invention physical pages that are subject to access by input/output relates to disabling only selected DMA operations in a physical I/O adapter in order to permit migration of data between physical pages that are subject to access by the physical I/O adapter.
2. Description of Related Art
According to a trend in computer systems, a system may be reconfigured while running without disrupting data processing. For example, with multiple operating systems running on the computer, a first one of the operating systems may be using a certain block of memory and there may be a need to reallocate the block of memory for use by a second one of the operating systems. Thus, the first operating system must first stop using the block of physical memory. As another example, a problem may be detected in a block of physical memory, in which case it may be desirable to remove the memory from operation so that it can be replaced. Thus, the data within a particular physical page may need to be moved or use of the physical page may need to be blocked for a period of time. If this block of memory is subject to access by I/O devices the problem of migrating or blocking the use of the physical page becomes difficult.
One method for migrating data that is subject to access by an I/O device is to temporarily but completely disable all arbitration that is done by the I/O adapter to which the I/O device is coupled in order to access the particular physical page. The process of arbitration is the first step taken during a DMA process. When arbitration is disabled, therefore, all DMA operations of the physical I/O adapter are disabled. Thus, for a short time period, all DMA operations for the physical I/O adapter that needs to access the data that is to be migrated are totally disabled when arbitration is disabled. During the short time period, the physical page data is then either migrated or updated. Once the migration or update of the physical page is complete, the DMA operations are once again enabled in the I/O adapter.
DMA operations include both data access operations to access the data as well as administrative services operations. These administrative services operations are typically executed in the background. Some physical I/O adapters require the ability to be able to execute administrative services operations in order to operate properly. For example, some physical I/O adapters use administrative services operations to access registers that are included in the particular physical I/O adapter. When arbitration is disabled in a physical I/O adapter as described above, all DMA operations, including data accesses and administrative services operations, are disabled. If the ability to execute administrative services operations is disabled even temporarily in an I/O adapter that requires these administrative services operations in order to function properly, the physical I/O adapter will enter an error state. This will cause the processor to cease processing.
Therefore, a need exists for a method, apparatus, and computer program product for disabling only selected DMA operations in a physical I/O adapter in order to permit migration of physical pages that are subject to access by the physical I/O adapter.